Device for limiting the supply of fuel to a diesel engine as a function of the engine exhaust temperature

ABSTRACT

THIS INVENTION PROVIDES A DEVICE WHICH IS EFFECTIVE AUTOMATICALLY TO LIMIT THE RANGE OF PERMITTED MOVEMENT OF A FUEL SUPPLY CONTROL ELEMENT IN RESPONSE TO A TEMPERTURE SENSED IN THE ENGINE EXHAUST GASES WHEN SAID TEMEPRATURE EXCEEDS A GIVEN THRESHOLD VALUE. OVERHEATING OF THE ENGINE WHEN WORKING IN RAREFIELD AIR IS THEREBY AVOIDED.

Sept. 20, 1971 FUSQ DEVICE FOR LIMITING THE SUPPLY OF FUEL TO A DIESELENGINE AS A FUNCTION OF THE ENGINE EXHAUST TEMPERATURE Filed Sept. 9,1969 United States Patent Ofice 3,605,711 DEVICE FOR LIMITING THE SUPPLYOF FUEL TO A DIESEL ENGINE AS A FUNCTION OF THE ENGINE EXHAUSTTEMPERATURE Oscar Fuso, Turin, Italy, assignor to Fiat Societa perAzioni, Turin, Italy Filed Sept. 9, 1969, Ser. No. 856,291 Claimspriority, application Italy, Sept. 19, 1968, 53,200/ 68 Int. Cl. F02d7/00 US. Cl. 123-140MC 3 Claims ABSTRACT OF THE DISCLOSURE Thisinvention provides a device which is effective automatically to limitthe range of permitted movement of a fuel supply control element inresponse to a temperature sensed in the engine exhaust gases when saidtemperature exceeds a given threshold value. Overheating of the enginewhen working in rarefied air is thereby avoided.

The present invention relates to a device for automatically reducing thesupply of fuel to a Diesel engine as a function of the temperature ofthe engine exhaust gases.

It is known that, as the altitude at which a Diesel engine is operatedincreases, the temperature of the exhaust gases gradually increasesbecause of the consequent rarefaction of the air which is mixed With thefuel. Such high exhaust gas temperatures could lead to dangerously hightemperatures for the components of the engine, and to avoid this it isnecessary to reduce the supply of fuel to the engine. It is clearlydesirable that such reduction of the fuel supply be effectedautomatically, and, moreover, should be discontinued when thetemperature of the exhaust gases has returned to an admissible value.The above mentioned reduction of fuel supply is particularly necessarywhen a Diesel engine operates at intervals at an elevated height.

An object of the present invention is to provide a device applicable toa Diesel engine and operable automatically to limit the supply of fuelto the engine when the temperature of the engine exhaust gases exceeds apredetermined value.

A further object of the invention is to provide a device of the abovementioned type capable of operating on the normal fuel supply regulatorin a diesel engine which can be set in two indicated positions in one ofwhich it permits a greater supply of fuel and in the other of which itpermits a reduced supply.

The characteristic feature of the device according to the invention liesin the fact that it comprises a temperature sensing element for sensingthe exhaust gas temperature to provide a signal which is referred in anamplifier unit to a reference level corresponding to a predeterminedthreshold temperature, and which is effective automatically when thesensed temperature exceeds said threshold temperature to actuate meansfor limiting the permitted range of movement of a mechanical controlelement which regulates the fuel supply to the engine, said means beinginoperative, permitting a full range of movement of the control elementwhen the exhaust gas temperature falls below a further predeterminedvalue.

Further characteristic features of the invention will be apparent fromthe detailed description which follows, given by way of non-limitingexample, with reference to the accompanying drawing, which illustratesschematically the application of a device according to the invention toa diesel engine.

In the drawing a fuel injection pump 1 of a Diesel engine is indicatedin broken outline. The pump 1 has a Patented Sept. 20, 1971longitudinally displaceable rack 2 for regulation of the fuel deliveryof the pump 1. The rack 2 projects beyond the exterior of the pump 1,its projecting part being surrounded by a tubular casing 3 in which aplunger 4 is mounted, for sliding movement. The plunger 4 is providedwith an axial abutment member comprising a projection 2a against whichthe rack 2 bears when in a position of maximum fuel delivery.

A spring 5 within the casing 3 urges the plunger 4 away from the rack 2towards an end closure, 3a, of the casing 3 and into engagement with anadjustable stop 6 which is screwed into said end closure 3a. When theplunger 4 is in engagement with the stop 6 the rack 2 has a maximumrange of movement and when the rack 2 abuts the projection 2a it permitsmaximum fuel delivery by the pump 1, the stop 6 being adjustable toallow variation of the maximum fuel delivery.

A temperature sensing element 8 is disposed in the exhaust gas outlet ofthe engine (not shown) and provides a signal, in this example, anelectrical signal, having an intensity proportional to the temperatureof the exhaust gases. This signal is passed to an amplifier unit 9 inwhich it is referred to a reference level corresponding to apredetermined threshold value of the exhaust gas temperature. Theamplifier unit 9 is connected to electrical supply lines 10 and controlsthe connection of the supply lines 10 to an actuator unit 11 operativelyassociated with the excitation coil of an electro-valve 12. Theamplifier unit 9 normally disconnects the actuator unit 11 from thesupply lines 10, but when the signal from the sensing element 8 exceedsthe reference level the amplifier unit 9 connects the supply lines 10 tothe actuator 11, energising the latter.

In the illustrated example the electro-valve 12 is a threeway valve,being connected to a fluid pressure supply conduit 13, an exhaustconduit 14-, and a conduit 15 which communicates with an internalchamber 7 of the casing 3, defined between the end closure 3a and theplunger 4, the plunger 4 and the chamber 7 constituting a fluid pressure actuator.

Under normal operating conditions of the engine, that is with thetemperature of the engine exhaust gases below the predeterminedthreshold level, the actuator 11 is inoperative and the electro-valve 12is in a first setting in which it connects the conduit 15 with theexhaust conduit 14: consequently the spring 5 displaces the plunger 4 tothe right (as viewed) and holds it against the stop 6. The rack 2 istherefore able to move over the maximum range permitted by the settingof the stop 6, so that the engine can be fed with the maximum charge offuel.

When the temperature of the exhaust gases reaches and exceeds thepredetermined threshold level the amplifier unit 9 places the actuatorunit 11 in connection with the supply lines 10, operating the unit 11and causing the electro-valve 12 to be placed in a second setting inwhich it interconnects the supply conduit 13 and the conduit 15, causingfiuid pressure to be supplied to the chamber 7. The plunger 4 isdisplaced to the left as viewed until it engages an internal stopshoulder 3a in the bore of the casing 3: in this position the plunger 4limits the excursion of the control rack 2 of the injection pump 1,thereby reducing the volumetric size of the maximum single charge offuel supplied to the engine by the pump 1.

Should the exhaust gas temperature return below the predeterminedthreshold value, the actuator unit 11 will be de-energised, and theelectro-valve 12 will return to its first setting, permitting normaloperation of the pump 1 to be resumed.

The exhaust gas temperature below which the device disposes the valve 12in its first setting can, if desired, be predetermined independently ofthe threshold temperature at which the device causes the valve 12 tochange from its first into its second setting.

The device according to the invention as described can be readilyapplied to existing diesel engines, by easy modification of themechanical controls thereof, by the simple mounting of the temperaturesensing element 8 in the exhaust gas outlet of the engine, and by theaddition of the amplifier unit 9, the actuator unit 11 and theelectrovalve 12 in the circuit of the servo system as described.

It will be appreciated that practical details of the describedembodiments may be varied Widely without departing from the scope of theappended claims.

I claim:

1. A diesel engine having a device for limiting the supply of fuel tothe engine according to the temperature of the exhaust gases, suchdevice comprising:

a movable mechanical control element which regulates the fuel supply tothe engine;

a temperature-sensing element for sensing the exhaust gas temperatureand providing an electrical signal representative of such temperature;

an amplifier and threshold unit in which said signal is referred to areference level corresponding to a threshold temperature;

limiting means actuatable by said amplifier and threshold unit when thesensed exhaust gas temperature rises above the threshold temperature andeffective when so actuated to vary the permitted range of movement ofsaid control element, said limiting means permitting a full range ofmovement of said control element while the sensed temperature is belowthe threshold temperature, said limiting means comprising a fluidpressure cylinder, an abutment member movable in said cylinder andadapted to operate on the control element, and a return spring urgingthe abutment member toward a position in which the abutment memberpermits a full range of movement of the control element;

an electro-valve;

a fluid supply conduit connected to said electro-valve;

a second conduit connected to said electro-valve and to said fluidpressure cylinder; and

an exhaust conduit connected to said electro-valve;

said electro-valve being controlled by said amplifier and threshold unitand being adapted to be actuated by said amplifier and threshold unit toconnect said fluid supply conduit to said second conduit and said fluidpressure cylinder when the sensed temperature rises above the thresholdtemperature, thereby to cause said abutment member to be displacedagainst the action of said return spring to limit the permissiblemovement of the control element; and said electro-valve being adapted tobe actuated by said amplifier and threshold unit to isolate the fluidsupply conduit from the fluid pressure cylinder and to connect saidsecond conduit and said fluid pressure cylinder to said exhaust conduitwhen the sensed temperature is below the threshold temperature.

2. An engine accordingto claim 1 wherein said fluid pressure cylinder isprovided with a stop shoulder to limit the movement of the abutmentmember in a direction against the force of said return spring.

3. An engine according to claim 1, including an adjustable stop fordetermining the position of the abutment member under the influence ofsaid return spring during normal operation of the engine.

References Cited UNITED STATES PATENTS 2,244,669 6/1941 Becker 123-14032,374,411 4/1945 Camner l23l40.3 2,720,751 10/1955 Kunz 39.28T 2,835,2405/ 1958 Braun 123-1402 MARK M. NEWMAN, Primary Examiner C. R. FLINT,Assistant Examiner US. Cl. X.R. I23140MP

